1. Igneous Rocks: Formed from the cooling and solidification of molten rock (magma or lava).
2. Sedimentary Rocks: Formed from the accumulation and cementation of sediments, like sand, mud, or shells.
3. Metamorphic Rocks: Formed when existing rocks (igneous, sedimentary, or even other metamorphic rocks) are transformed by heat and pressure.
Note: There is no fourth category for classifying rocks based on how they formed. However, geologists might use additional criteria to further classify rocks within these three categories. For example, igneous rocks can be classified based on their mineral composition and texture, while sedimentary rocks can be classified based on the type of sediment they are made of.
